import React from "react";
import ReactDOM from "react-dom/client";
import "./index.css";

// class Square extends React.Component {
//   constructor(props) {
//     super(props);
//     this.state = {
//       value: null,
//     };
//   }
//   render() {
//     return (
//       <button
//         className="square"
//         onClick={() => this.props.onClick()}
//       >
//         {this.props.value}
//       </button>
//     );
//   }
// }
//可以将只有一个render方法的组件写成下面的样式
function Square(props) {
  return (
    <button className="square" onClick={props.onClick}>
      {props.value}
    </button>
  )
}
//当我们把 Square 修改成函数组件时，我们同时也把 
// onClick = {() => this.props.onClick()} 改成了更短的
// onClick = { props.onClick }（注意两侧都没有括号

class Board extends React.Component {
  renderSquare(i) {
    return <Square
      value={this.props.squares[i]}
      onClick={()=>this.props.onClick(i)}

    />;
  }

  render() {
    return (
      <div>
        {/* <div className="status">{status}</div> */}
        <div className="board-row">
          {this.renderSquare(0)}
          {this.renderSquare(1)}
          {this.renderSquare(2)}
        </div>
        <div className="board-row">
          {this.renderSquare(3)}
          {this.renderSquare(4)}
          {this.renderSquare(5)}
        </div>
        <div className="board-row">
          {this.renderSquare(6)}
          {this.renderSquare(7)}
          {this.renderSquare(8)}
        </div>
      </div>
    );
  }
}

class Game extends React.Component {
  handleClick(i) {
    const history = this.state.history.slice(0,this.state.stepNumber+1);
    const current = history[history.length - 1];
    const squares = current.squares.slice();
 //创建了一个副本,因为数据不可变性极其重要
    if (calculateWinner(squares) || squares[i]) {
      return;
    }
    squares[i] = this.state.xIsNext ? "X" : "O";
    this.setState({
      history: history.concat([{
        squares: squares,
      }]),
      stepNumber:history.length,
      xIsNext: !this.state.xIsNext
    });
  }
  jumpTo(step) {
    this.setState({
      stepNumber: step,
      xIsNext: (step%2)===0,
    })
  }
  constructor(props) { 
    super(props);
    this.state = {
      xIsNext: true,
      history: [{
        squares:Array(9).fill(null),
      }],
      stepNumber:0,//当前正在查看哪一项历史记录。
    };

  }
  render() {
    const history = this.state.history;
    const current = history[this.state.stepNumber];
    const winner = calculateWinner(current.squares);

//历史记录
    const moves = history.map((step, move) => {
      const desc = move ?
        'Go to move #' + move :
        'Go to game start'
      return (
        <li key={move}>
          {/* 每一个li都应该添加key 与vue类似 */}
          <button onClick={() => this.jumpTo(move)}>{desc }</button>
        </li>
      )
    })

    let status;
    if (winner) {
      status = 'Winner:'+winner;
    } else {
      status ='Next player: ' + (this.state.xIsNext ? 'X' : 'O');
    }
    return (
      <div className="game">
        <div className="game-board">
          <Board 
            squares={current.squares}
            onClick={(i)=>this.handleClick(i)}
          />
        </div>
        <div className="game-info">
          <div>{status}</div>
          <ol>{moves}</ol>
        </div>
      </div>
    );
  }
}

// ========================================

const root = ReactDOM.createRoot(document.getElementById("root"));
root.render(<Game />);

function calculateWinner(squares) {
  const lines = [
    [0, 1, 2],
    [3, 4, 5],
    [6, 7, 8],
    [0, 3, 6],
    [1, 4, 7],
    [2, 5, 8],
    [0, 4, 8],
    [2, 4, 6],
  ];
  for (let i = 0; i < lines.length; i++) {
    const [a, b, c] = lines[i];
    if (squares[a] && squares[a] === squares[b] && squares[a] === squares[c]) {
      return squares[a];
    }
  }
  return null;
}